The long-term objective of this project is to understand the function of the ocular secretory IgA system. Specific aims include characterization of rat tears by (1) determining the monomeric/polymeric IgA components and amount of free secretory component in tears and other secretions of male and female rats; (2) studying the influence of age and sex on the IgA and SC content in rat tears; and (3) studying the contribution of serum to tear immunoglobulins by infusion of 125I-labeled proteins and antibody into rats. The cells of the rat ocular secretory immune system will be studied by (4) determining the T and B lyymphocyte and Ia+ cell population of the exorbital gland and conjuctiva; (5) studying the influence of age and sex on the number of immunoglobulin-containing cells in exorbital gland; (6) evaluating the effect on the ocular system of age at which conventionalization occurs in germ-free rats, (7) studying the effect of excluding the topical ocular antigenic stimulation, by tarsorrhaphy of one eye, on the numbers of immunoglobulin-containing cells in the exorbital gland; and (8) characterizing the synthesis of IgA and SC by rat exorbital gland and conjunctiva in tissue culture. The ocular secretory IgA response to immunization will be studied by (9) using the ELISA technique to measure the occurence of natural antibodies in rat tears; and (10) developing methods for eliciting antibodies in tears by local and remote stimulation. The human ocular sIgA system will be studied by (11) determing by molecular sieve chromatography the characteristics of IgA and SC in tears; and (12) by the ELISA technique measuring the relative concentrations in tears, saliva, and serum of antibody to local (olcular) and remote (oral) bacteria; and (13) characterizing cells of the lacrimal gland, accessory lacrimal gland, and conjunctiva for their IgA1 and IgA2 content by immunofluorescence. The health relatedness of the projects: understanding the ocular sIgA system will allow development of methods to influence the system for the health of the eye.